When channel-coded data is transmitted in a wireless communication system, coded data is divided into a plurality of bandwidths and the signal power is distributed to the bandwidths so that the communication channel capacity is increased. In addition, the transmission power is controlled on a time basis in such a way that the average power becomes larger when the channel quality is poorer so that the quality of each code word is stabilized. Alternatively, the coding rate is controlled in such a way that the data rate is decreased when the channel quality is poorer.